faccessat() - Unix, Linux System Call

NAME

faccessat - change permissions of a file relative to a directory
file descriptor

SYNOPSIS

#include <unistd.h>

int faccessat(int dirfd, const char *path, int
mode ", int " flags );

DESCRIPTION

The faccessat() system call operates in exactly the same way as
access(2),
except for the differences described in this manual page.

If the pathname given in
path is relative, then it is interpreted relative to the directory
referred to by the file descriptor
dirfd (rather than relative to the current working directory of
the calling process, as is done by
access(2)
for a relative pathname).

If the pathname given in
path is relative and
dirfd is the special value
AT_FDCWD, then
path is interpreted relative to the current working
directory of the calling process (like
access(2)).

If the pathname given in
path is absolute, then
dirfd is ignored.

flags is constructed by ORing together zero or more of the following values:

Code

Description

AT_EACCESS

Perform access checks using the effective user and group IDs.
By default,
faccessat() uses the effective IDs (like
access(2)).

AT_SYMLINK_NOFOLLOW

If
path is a symbolic link, do not dereference it:
instead return information about the link itself.

RETURN VALUE

On success,
faccessat() returns 0.
On error, -1 is returned and
errno is set to indicate the error.

ERRORS

The same errors that occur for
access(2)
can also occur for
faccessat(). The following additional errors can occur for faccessat():

Tag

Description

EBADF

dirfd is not a valid file descriptor.

EINVAL

Invalid flag specified in
flags.

ENOTDIR

path is a relative path and
dirfd is a file descriptor referring to a file other than a directory.

NOTES

See
openat(2)
for an explanation of the need for
faccessat().

CONFORMING TO

This system call is non-standard but is proposed
for inclusion in a future revision of POSIX.1.

GLIBC NOTES

The
AT_EACCESS and
AT_SYMLINK_NOFOLLOW flags are actually implemented within the glibc wrapper function for
faccessat(). If either of these flags are specified, then the wrapper function employs
fstatat(2)
to determine access permissions.